Detection and quantification of CSF malignant cells by the CellSearch^® technology in patients with melanoma leptomeningeal metastasis

Melanoma is the most frequent solid tumor associated with leptomeningeal metastasis (LM). The usual diagnostic tools, that is, cytomorphological assessment of cerebro-spinal fluid (CSF) and gadolinium-enhanced MRI of the entire neuraxis both lack effectiveness. The CellSearch^® Veridex technology for the detection of circulating tumor cells (CTC) in blood was designed for the follow-up and prognosis of breast, prostate, colorectal, and lung cancer, which express EpCAM markers. We have previously adapted this technology to detect malignant cells in the CSF of breast cancer LM. Our objective here was to check if this technology would also allow the detection and the enumeration of CTC in the CSF of melanoma patients presenting with LM although melanoma does not express EpCAM markers. On the occasion of the intrathecal treatment of LM in 2 melanoma patients, 5 mL of CSF and 7.5 mL of blood were collected on CellSave^® Preservative Tubes and analyzed within 3 days after CSF sampling using a melanoma-dedicated kit. The CellSearch^® Veridex technology was then adapted to direct enrichment, enumeration, and visualization of melanoma cells in the CSF. CD146+, HMW-MAA+, CD34−, and CD45− cells with typical morphology could be observed and enumerated sequentially with reproducible results, corresponding to CSF melanoma cells (CSFMC). In contrast to the current gold standard cytomorphological analysis, this new approach allowed a precise quantification of CSFMC in all samples concomitantly analyzed. This methodology, established on a limited volume of sample and allowing delayed processing, could prove of great interest in the diagnosis and follow-up of melanoma patients with LM.